1. Field of the Invention
The present invention relates to navigation systems and more particularly, to route calculation based on propulsion-related operating parameters.
2. Related Art
Navigation systems for vehicles include route determination functions that generally determine routes from a starting point to a destination with the objective of minimizing either driving distance or driving time. Neither objective necessarily provides the most energy-efficient route. As the costs of energy and the focus on environmental conditions increase, drivers are becoming increasingly interested in taking the most energy-efficient route. Route determination based on energy efficiency makes use of functions and resources not normally associated with navigation systems such as predicting the energy consumption for road segments on alternative routes.
One difficulty with predicting fuel consumption for a given route is that fuel consumption varies according to the vehicle. The average fuel consumption varies between different makes and models. Even for a given model, the fuel consumption varies for different types of engines, different tires, different vehicle accessories, and other possible variables. Further variations in fuel consumption also arise from the driving style of the driver, and from environmental conditions, such as the type of road being traveled.
The variety of variables that factor into a vehicle's fuel consumption make it impractical as a function in a typical vehicle navigation system. Complex models for vehicles have been proposed. However, such models are based on the use of a large number of fixed, vehicle-specific parameters. These parameters may not be generally available for all types of vehicles and may not be available to the provider of the vehicle navigation system. The complexity and their use of an extensive parameter space make these models impractical for use in portable or dashboard-mounted navigation systems. The complexity is magnified by implementation for different vehicles and vehicle models. Conventional vehicle navigation systems are not equipped to determine energy-efficient routes with sufficient accuracy.
Accordingly, a need exists for a method that improves the estimation of propulsion-related operating parameters, such as fuel or energy consumption, or CO2 emission, of a vehicle for a road segment. A need also exists for a vehicle navigation system capable of performing such estimation.